1. Field of Invention
This invention is related to a hinge structure of a case, intended to join a case body and a lid together by means of a hinge in a manner capable of opening, turning, and closing the lid, and in particular, to a hinge structure that prevents a shearing force from acting onto the hinge shafts.
2. Description of Related Art
A compact case is used to take along a cosmetic material, such as a foundation, and the case includes a case body in which to contain a cosmetic material, and a lid that covers the top surface of the case body. Because of lightness in weight, high processability, and low cost, many of the compact cases are made of synthetic resins.
As the synthetic resin compact cases for cosmetic use, there are known those compact cases in which the first hinge connector or connectors are combined with the second hinge connector or connectors. These connectors are disposed at the rear of the case body or the lid, and are provided with a hole or two holes into which a hinge shaft or two shafts are inserted to join the case body and the lid together in a manner capable of opening the lid, turning the lid from the position on the case body, and then closing the lid.
When a cosmetic compact case is used, the lid is turned around, with a hinge shaft or shafts serving as the axis or axes of rotation, and the front side of the lid is raised away from the case body. The lid is then stopped by the rear end of the case body at one point where the movement of the lid comes up to the limit of rotation.
Sometimes hinge shafts were broken if an external force acted on the lid in the lid-opening direction at the limit of rotation where the lid could no longer continue to turn relative to the case body. At those times, strong forces acted as shearing forces on the hinge shafts in which the portion pushed by the external force under the leverage served as the power point, while the hinge shafts that joined the case body and the lid together served as the point of action.
The case body and the lid are usually joined together with a hinge to improve the handling ability. Hinge shafts, one of the hinge components, are generally made of a metallic material because high mechanical strengths, such as toughness, are required for the hinge shafts.
However, in recent years, there was a greater demand than ever for the separate collection and disposal of synthetic resin products from a resources recycling point of view. If this demand should be met in compact cases, it is required to remove the metallic hinge shafts from the cases.
The hinge connection must not be easily slipped away. The lid should be securely held at any opening posture relative to the case body. Thus, the hinge shafts are often fitted tightly to shaft holes so that the shafts may have a frictional resistance of a certain level or higher between the shaft and the shaft hole. Therefore, it was difficult to take the hinge shafts out of the shaft holes. There was little choice but to break the hinges for the separate collection.
In the conventional art, P1999-290118 and P1999-285411 were disclosed to solve this problem of separate collection and waste disposal. Proposed in these patent applications were a compact case including a case body, a lid, and hinge pins, all made of synthetic resins. (See FIGS. 5-7.)
The hinge pins of synthetic resins disclosed in the conventional art have advantages in that the compact cases can be lightweight, that no separate collection and disposal are required because the hinge shafts, the case body, and the lid are made of the same materials, and that the production cost is less expensive. However, the hinge pins of synthetic resins have problems in that, because these pins are inferior to metallic ones in their rigidity and strength, the resinous pins cannot withstand the shearing force applied on the hinge pins, and that sometimes they are easily broken.
As shown in FIGS. 10-12, the cosmetic case of P1999-285411 includes a container 112 of a synthetic resin in which to contain a cosmetic material and a synthetic resin cover 114 to open or close the case body 112. Hinge blocks 116 and 118 are respectively disposed at the rear of the container 112 and the cover 114. Hinge pins 120 made of a synthetic resin are the axis of rotation for the cover 114 to turn relative to the container 112 and are inserted through the pinholes inside the hinge blocks 116 and 118. Collar flange 126 and circular boss 128 are disposed between the respective hinge blocks 116 of the container 112 and the hinge block 118 of the cover 114. The hinge pins 120 are inserted through these blocks so that the flange 126 and the boss 128 surround the hinge pins 120 and are engaged firmly with each other in a manner rotatable from each other.
The collar flange 126 is provided with a cut 130 through which the circular boss 128 is inserted in the radial direction.
Although, in that conventional art, synthetic resin pins have a lower strength than the metallic pins have, the breakage in the hinge pins 120 of a synthetic resin is prevented by allowing the collar flange 126 and the circular boss 128 to receive strong shearing forces that may act on the hinge pins 120.
When the circular boss 128 is fitted into the collar flange 126, the boss 128 is inserted through the cut-out section 130 in the flange 126. In this way, both of the boss 128 and the flange 126 are easily engaged with each other, and the circular boss 128 never slips away from the collar flange 126. Thus, the cover can be smoothly rotated on the hinge pins 120 that serve as the axis of rotation in the movement relative to the case body.
However, the above-described conventional art had a problem in that the width of the cut-out section 130 of the collar flange 126 had to be forcibly expanded and deformed up to the width equal to the diameter of the circular boss 128. This deformation of the hinge block 118 may lead to a risk of breakage.
A possible measure taken to avoid the breakage of the hinge blocks is to utilize a soft, highly deformable synthetic resin. However, if a soft synthetic resin is used for the hinge blocks or for the container, the poor feel of the material will result, and commercial value will drop. In addition, a problem arising from a soft material is that the hinge connection disrupts the stability, and often the opening/closing operations get out of order.
If a cut-out section is formed underneath the hinge blocks, as in conventional art, the cut-out is open downward when the compact case is carried in the state where the cover remains closed. If an external force acts unexpectedly on the cover in the direction that the cover is raised at the rear side, this external force cannot be received by the collar flange and the circular boss, but acts directly on the hinge pins as a shearing force. Thus, the breakage of hinge pins causes a problem.